nasbackup.sh: add optional backup compression via -c flag - #12844
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Add -c/--compress flag that produces compressed qcow2 backup files, reducing storage usage on the NAS backup target. For stopped VMs: passes -c to qemu-img convert directly. For running VMs: re-compresses push backup output with qemu-img convert -c after the backup job completes. Compression is off by default to preserve existing behavior and avoid increased CPU usage on hosts that don't need it. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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March 17, 2026 19:24
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Codecov Report✅ All modified and coverable lines are covered by tests. @@ Coverage Diff @@
## 4.20 #12844 +/- ##
=========================================
Coverage 16.24% 16.25%
- Complexity 13411 13412 +1
=========================================
Files 5664 5664
Lines 500463 500463
Branches 60779 60779
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+ Hits 81308 81334 +26
+ Misses 410059 410035 -24
+ Partials 9096 9094 -2
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Pull request overview
Adds an optional -c/--compress flag to nasbackup.sh so NAS backups can be written as compressed qcow2 images (default remains uncompressed), reducing backup storage usage.
Changes:
- Introduces -c/--compress CLI flag and wires it into the backup workflow.
- For stopped VMs, conditionally adds -c to qemu-img convert.
- For running VMs, performs a post-backup recompression pass over generated .qcow2 files.
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scripts/vm/hypervisor/kvm/nasbackup.sh
| for disk in $DISK_PATHS; do | ||
| volUuid="${disk##*/}" | ||
| qemu-img convert -O qcow2 $disk $dest/$name.$volUuid.qcow2 | tee -a "$logFile" | ||
| qemu-img convert $([[ "$COMPRESS" == "true" ]] && echo "-c") -O qcow2 $disk $dest/$name.$volUuid.qcow2 | tee -a "$logFile" |
Comment thread
scripts/vm/hypervisor/kvm/nasbackup.sh
| for img in "$dest"/*.qcow2; do | ||
| [[ -f "$img" ]] || continue | ||
| local tmp_img="${img}.tmp" | ||
| if qemu-img convert -c -O qcow2 "$img" "$tmp_img" 2>&1 | tee -a "$logFile"; then |
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scripts/vm/hypervisor/kvm/nasbackup.sh
| [[ -f "$img" ]] || continue | ||
| local tmp_img="${img}.tmp" | ||
| if qemu-img convert -c -O qcow2 "$img" "$tmp_img" 2>&1 | tee -a "$logFile"; then | ||
| mv "$tmp_img" "$img" |
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… integrity check Adds four optional features to NAS backup operations, configurable at zone scope via CloudStack global settings: - Compression (-c): qcow2 internal compression of backup files Config: nas.backup.compression.enabled (default: false) - LUKS Encryption (-e): encrypt backup files at rest using qemu-img Config: nas.backup.encryption.enabled (default: false) Config: nas.backup.encryption.passphrase (Secure category) - Bandwidth Throttle (-b): limit backup I/O bandwidth via virsh blockjob for running VMs or qemu-img -r for stopped VMs Config: nas.backup.bandwidth.limit.mbps (default: 0/unlimited) - Integrity Check (--verify): qemu-img check after backup creation Config: nas.backup.integrity.check (default: false) All features are disabled by default and fully backward compatible. Settings are read from zone-scoped ConfigKeys in NASBackupProvider, passed to the KVM agent via TakeBackupCommand details map, and translated to nasbackup.sh CLI flags in LibvirtTakeBackupCommandWrapper. Changes: - nasbackup.sh: add -c, -b, -e, --verify flags with encrypt_backup() and verify_backup() helper functions - TakeBackupCommand.java: add details map for passing config to agent - NASBackupProvider.java: add 5 ConfigKeys, populate command details - LibvirtTakeBackupCommandWrapper.java: extract details, build CLI args, handle passphrase temp file lifecycle Combines and supersedes PRs apache#12844, apache#12846, apache#12848, apache#12845
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Summary
Motivation
NAS backup storage fills up quickly with large VM disks. qcow2 compression typically achieves 40-60% size reduction with minimal CPU overhead, extending backup retention without additional storage.
The -c flag can be passed by the CloudStack agent when the admin enables compression in the backup repository settings, giving per-repository control.
Test plan